[willamette-fcst] Forecast - Thursday, March 4th, 2010

[Willamette Valley Ag/Burning Forecast]

Daily Smoke Management Forecast




Oregon Department of Agriculture
Smoke Management Program
Weather Outlook and Field Burning Advisory for Willamette Valley Growers and Fire Districts.

Issued: 
     Thursday, March 4th, 2010 at 9:00am.

Burn Advisory:
     Recommended burn times for agricultural burning are from 12:00pm until 4:00pm.
     Straw stack burning is allowed from 12:00pm until 4:00pm.

Weather Discussion:
     A split-flow jet stream pattern is continuing to weaken
     weather systems, as they approach the Oregon coast...sending
     the bulk of the rain and mountain snows south into
     California.  A fairly potent weather system moved across
     California on Wednesday, with lots of clouds by not a lot of
     precipitation making it northward over Oregon.  Rainfall
     totals over the Willamette Valley ranged from just a trace
     to nearly one-quarter of an inch.  Meanwhile, near the California
     border, Medford picked up nearly one-half inch of rain.

     The storm pushed eastward, across Nevada, overnight, sending
     significant moisture just north of the Oregon border. Rome,
     in southeastern Oregon, picked up over one-inch of
     water-equivalent precipitation, with ODOT road cameras
     revealing snow-covered ground and near-freezing temperatures
     there this morning.

     Residual moisture, combined with partial clearing overnight,
     led to the formation of low clouds and areas of fog across
     the western valleys this morning. Visibilities were locally
     reduced to less than one-quarter of a mile across much of
     the northern Willamette Valley.  Overnight temperatures fell
     to near the freezing mark in some sections of the Willamette
     Valley.  Hillsboro was one of the colder spots, with a
     minimum of 33 degrees.

     Mid-morning satellite imagery showed considerable low clouds
     blanketing the interior valleys of western Oregon, with
     clearing skies from the coast range westward to the beaches.
     High clouds from the next weather system were advancing
     towards the coastline.  Temperatures ranged from a foggy 37
     degrees, in Hillsboro, to a partly sunny 46 degrees in
     Eugene. The ODA surface analysis showed high pressure
     building into western Oregon with flat pressure gradients
     and light winds.

     The air aloft is as cold this morning as we have seen in
     awhile.  The freezing levels were measured over Medford and
     Salem at just 3400 and 4700 feet respectively, and ODOT road
     cameras showed a light dusting of new snow over the Cascade
     passes.  A transitory ridge of high pressure will help skies
     to at least partially clear across the western valleys this
     afternoon, with mostly sunny skies giving way to increasing
     high clouds along the beaches.  A light south wind will
     develop, ahead of the next weather system, helping afternoon
     temperatures climb into the mid 50s across the Willamette Valley.

Surface Winds:
     SSE 0-5 this morning, S 3-6 this afternoon.
Transport Winds:
     S 5 this morning, SSW 6 this afternoon.
Atmospheric Ventilation Conditions:
     Maximum mixing height today will be near 3500 feet.  Ventilation index 21.
High Temperature:
     Salem\'s high temperature today will be near 55.
Humidities:
     Minimum relative humidity will be near 61%.
Sunrise/Sunset:
     Salem sunset tonight: 6:04pm; sunrise tomorrow: 6:43am.

Extended Outlook:
     On Friday, a weather system dropping into the region, from
     the Gulf of Alaska, will also encounter the split-flow
     pattern in the jet stream offshore and move mainly into
     California.  Some light rain is possible...mainly along the
     coast and across southern Oregon.  A weak ridge of high
     pressure will dry things out for the first half of the
     weekend with a little sunshine.

     A change to a stormy and cooler weather pattern is forecast
     for next week.  A cold front should spread rain back onshore
     Sunday afternoon, and across western Oregon by Sunday
     evening.  This system has colder air aloft associated with
     it, so snow levels will likely drop to below the Cascade
     passes.  Showers will taper off Monday, with the lowest snow
     levels we\'ve seen in many weeks.  After a brief break, early
     Tuesday, another cold weather system will bring more valley
     rain and much-needed mountain snow Tuesday night and
     Wednesday.  Yet another system is forecast to bring rain and
     blustery conditions onshore Thursday, followed by cooler and
     showery weather next Friday.

Fri (05 Mar):  Mostly Cloudy.  Chance of Rain...Mainly South.  Snow Level 4000 Feet.  38/57

Sat (06 Mar):  Becoming Partly Sunny and Mild.  37/60

Sun (07 Mar):  Rain Developing in the Afternoon.  Snow Level Dropping to 3-4000 Feet.  36/53

Mon (08 Mar):  Decreasing Showers.  Snow Level 2500 Feet.  35/49

Tue (09 Mar):  Increasing Clouds.  Chance of Rain Late.  Snow level 4000 Feet.  31/51

Wed (10 Mar):  Rain Turning to Showers.  Snow Level Near 3000 Feet.  38/51

Thu (11 Mar):  Rain Developing and Turning Blustery.  Snow Level Rising To 5000 Feet.  36/52

ODA Meteorologist
weather at oda.state.or.us